Telephone ring-bak or reverting-call system.



G. L Kl-MBALL; TELEPHONE RING BACK OH REVERTING CALI `SYSTEM.'

APPLICATION FILED IUNE 23.1909.

' Patented Feb. 20,1917.

Mwmk k@ @We G. E. KIMBALL. TELEPHONE RING BACK 0R REVEHTING CLL SYSTEM f APPLICATION FILED JUNE 23.1909. 1,216,461. Patentedlveb. 20,1917.

2 SHEETS-SHEET 2.i

t im STATES PATimoFFIeE.

GEORGE E. KIMBALL, F ROCHESTER, PENNSYLVANIA', ASSIGNOR TO .ATOMATIC ELECTRIC COMPANY, 0F CHICAGO, ILLINOIS, A C( lEPURATION OF ILLINOIS.

iniwhieh provision is made for enabling a vfsiibsi'riber to eall and .ring back on the call' ing line to signal another subscriber thereon.

Systems of thislind, employing auto- 15 matie switches at the central station, are

sometimes referred to as reverting call sys-` tems, because oif the fact that thecalhif it befor a party line siibseril'ier, may revert to i tjlieiline'of tl'ie calling si'ibseriber, so that two snl`iseribers on the same line may. converse ,-\\f'itli eaehirit-her. v Olijeetsof my invention are to provide an improved ring-bark or reverting call arrangement whereby one subscriber may call 25,'aiiotlier on the saine line; to provide ali-arrangeineut whereby the party line re- .leased from the ring-back arrangement by 'luthi-openiugofthe line at lthe, callingI and ""ealleil siibs'tatiolis thereong'and to provide eertain details and features o'filn )rovenient ftend'ii'igtorinerease,the general e eieney olf.`

,cular'eharaeteiz Y a systeiii -ojf this pa-i l nl viiiventioii eonsists in lmatters hereinafter set-forth and elaiuieil.

Y Pn the argoinpanying di a\\"ingsFigure lv )res-"ents (llagrauiiiiatieally an automatic' lim.l system,l enihodying,v the prineiples i A used` 4for talking; the siilistationffil AV and A' fare allotted to the line "which terminates tit. -'tlie 'eventi-al oilee in` the selector. swlteh .'iiifivhieh -at l) therefis shown in y improved ring-bark Vairaninine-nt by ini-ans of' which a 445- snbsei'iliei of'a' party line may eall and ringbaek, iipon his own line; inwhieh a ventral battery toitalking and operating',purposes 'isslionni "atw'li having its 'positive terminal [preferably grounded'at (l: and inwhieh itt -I)1 ther`e represented (li-.inra:tunatiiallfi i,

'eenti'al ringer generator. i

lii Fi". 2 is shown :i modified torni of the ringliaek ,or reverting all arrangement shown iii Fig. l.

l* ig. 3

Specification of Letters Patent "tlie;i'oregn'iing'and other iisefnl ends invention,v in wliiehi'entral,energyis represei-its iliagraiiiniatieally the TELEPHONE RING-BACK 0R REVERTIN -CALL SYSTEM.

` Patent-ed Fei). 20,1917.

Application led June 23, 1909. Serial 1 lo. 503,816.

conneetor switeh l" by means of' which subscribers mi y establish 'connection with different lines i' The substation' A2 is similar tothe substations A and A. and, as shown, has al lotted to it the first selector H which is the same as th: first selector CQ; It will be unf derstood tllat in the central office, in addition to tlre lfirst selector and connector switches, which are of the general type shown iuti'nited States Letters Patent Nos.

815,321 and 815.176, issued lllareh 13, 1906,.

to Keitli.,.llriel son and llrieksi'in., there may be added second selertor switehes', lor even third or fiurth seleetors,ete..v to inei'ease the capacit y of the system. In that ease the bank levels of the first seleetorswiteliesare provided 'v ith trunk lilies leadingto second selector switches,I and likewise from the seeoIid seleetir bank leveltriink lines leading to the connector S\\-'itehes,l or to other seteni one level, either in the first" or 'serond selector bank, may be allotted to signaling b`y the; nso of the devices I),--that is,4 the.

trunk linen from the eontaets'in :some eertain level, instead of4 leadingjto al seleetor or eonneetor switch, lead to ringliaek arraiige-- ments I.) Figi 1) fand a suliserilier., after having Vproper-'lv operated the eentral oiliee swlteh or switches and'festablished eonneevtion with said ring-haelt lev'elg-fnin'y eanse Yrnigglnle;l ein-rent to pass bat-k over his` own line' to'sigiial some other suhseriber oreupying the saiiiel'iiie with him. `ln `l"i lthis ringdiaek iirrangemeiit is shown allotted to i the seeondlevel: of the first seleetordianks. Any level lion-ever, either of the irs'tor ,seeoiidsel :etor banks,l ymaybe equipped in the saine i ia'nner. Y

rllie sub station` A may be of any Suitable. or apiriroved ti vpe.'l`he substations `A and A. like :iibstations usually employed in eonneetioii with switches of the aforesaid type` are `aeh 'pro'rideilj 'with a dial which the slibser hers operate for sending;- impulses over the lines to opeHiti-e'` lheswitehes at the ee'iitral ol'ee, lilai-li .substation is also provided with thel usual. l[ellephone@switeh hook thi-:sugli t ie niediuin;4 of wliiih the fsiibstzvy tion' fi-ouml e'iijeuit. the release eirfeuit-alid the prima seeondaiwf and ringing eirenits ai feriti-oiled.4 The subs-tations of *he type iii eonneetion with which l have elected to illustrate ny inventioneaeh 4comprise a rel y ceiver 2 and a switch hook Bil-for controlling the substation circuits, which controlling operations are accomplished vthrough the medium of any 'suitable means, such as the cam arms 4, 5 and 6. As the switch hook is lowered theV cam arm 4 momentarily presses the release springs 7, Sand 9 into engagement, whereby the 'substation line conductors may be grounded'simultaneously. When'theswitch hook is down the cam arm 5 maintains a conta-ct betweenV the springs 'I 10 and 11, thereby bridging the ringer 12 in series with the condenser 13 across theline. The substation ground circuit is norwipers and 46,respective1y, and the private wiper 47," lThe slde switch is Well known -andcomprises the side switch wipers y 48, 49, and 51 which normally occupy the contact points'53, 5 4, 55 and56, respectively; In the second position the Wipers rest on the' contact points' 57, 58,59 and 60, respectively,

mallybroken between the 'ground springs when 'sald springs are together ground isprovided to 7, as is usually the case in telephones of this theground post 16 and to the release spring type. The said substation comprises the` usual transmitter 17 and induction coil 18,

thev latter having the primary Winding 19' substation is provided with an impulse'wheel 25 that is secured tothe shaft 26, which impulse wheel carries on its periphery theso-f locksA the dog switch hook, i .For operatingA theimpulse springs 21 and 22 theA called/ vertical impulse teeth 27" and oneA rotary impulse tooth 28". The saidimpulse i -teeth are so arranged that when the dialis drawn down,the impulse'springs 21 and 22 are. not carried into contactwith the ground post 16; but as the dial. returns,1firs`t the vertical teeth force -the vertical impulse spring 21 into engagement withthe ground lpost 1 6, and after they have completed their work therotary impulse tooth ,operatesthe rotary impulse 'spring 22. In this operation the subscribers vertical line conductor 27 is rstgiven a number of ground impulses, and then the rotary 'line conductor 2.8' is- -givenone ground impulse; It will be seen that as long vasthe Idial is out'of normal .position the'censtructionis such that the-dog 23 permits the primary circuitsprings 29 and 30 to separate, thus preventing theiimpulses that are deliveredl to eitherline .conductor f nompassing to the other. A' calling subscriber 'may slgnal a. vcalled subscriber by, 'means of the push button 31l which, when pressed, carriesv the spring 32 'o'ut of' engageinent with the contact 'point 33 'and into en-I` -gageinent with the eontact point 34, wheref by the verticalline conductor 27 is grounded.

'The first selector switch shown' at 'C' is conductors 176, 7 7 andv78, over which ineo'mand in theA 'third position the contact points 61, 62, 63 and 64 are engagedbytheir re;

'spective wipers. Through'the medium of the vertical line relay 65, and while theside switch is in first position, the subscriber con-V trols the vertical magnet 66,-which latter opto rai'setheswitch shaft and wlpers 45,. 46 and 47 vertically. .By means of the rotary line relay 67 the subscriber .controls the private magnet 52, and, therefore,'the side switch. While the side switch 4is in second position the rotary magnet68,which operates to carry the4 switch shaft and wipers 45,46 and 47' in a rotarydirectiom is energize'd. The vertical and rotary line, relays and 67, acting conjointly, provide means whereby the subscriber controls the release magnet' 69 lwhile the side switchdsfin thfirst 'or second position. ,T -th tor is of the trunk-release type`,the release is controlled by means of the back-release' relay 70 irom'the next switchwith which a connection is at that' time established,

throuigh the private wiper47. Thebri'dge#V relay 71 is provided to open the con-- cut-o nectionbetween the line relays 65 and 67 and between 'said relays and battery B when the line associated therewith is called. This yis fdesirable, because-if the relays," are not disconnected from each other and :battery the ringing'current for signaling the subscriber may operate either. or both of the withthe switch. I t'i's alsol desirable to remove: the bridge formed through the said voice relays from across the line to give tl currents as clear a path as pessible. l addition, the first selector is providedwith' a ,normal arm 72 which, when the 'shaft is raised, permits the spring 7 3 toppass-out A e' switch passes to third posit1on,.tl;gs1nce the selecof engagement with the spring 74 'and into 1 engagementwith thev spring v75. Thenormal ing calls are made, terminate in the' con` 'Bhe ring-back or revertingcall arrange'-` met shown at Drcomprises the vertical and rotary line relays 79 and 80 connected in series withth'e-windingsl and 82 ofthe.

mmals.- `A resistance coil 84 isprovi di .jowaof current through the back releaseredayv .O of the selector, which'relay is of one.- constructed as follows: The switch shaft (not show/li) carries the verticalfand rotary lialf ohm resistance. The ringer relay-85.

.UPOII energizing operates to brldge'the ter# ter- .nector banks, as is usually the casein sysi tems of this general. character.

125 '-the trunk-release circuit to cut down `th y relays 65 and 67 and cause seme-interference 5 /tary line relays 12T and '1 selectors, :circuits i The ries the line wipers 121% shown The function of the vertical magnet 129 is togivethe'shaftand shaft wipers a vertical irio'tion, and the rotary magnet 130 imparts .to the shaft `and 'shaft wipers a 'rotaryv or circularl mot-ion. The rotary line relay 128 controls the pri Vat-e'magnet 131, which latter, under certain "conditions, controls in turn the vertical and rotary i'iiagnets 129 and 130, tlie'releasc magnet l32and also the side switch wipers '134,v 135, 136 and 15i7. The side' switch of the connector, like the side switch oftl'ie selector, hasI a normal or first position, a second and a third position. The release magnet 132 is also controller] by the verti `-al and rotary line relays 127 vand 128 eonjoiiit'ly. By the use of the condensers 138 and '13!) iu the connecto'iI the circuit through across the will te assumed that subscriber 'it is" divided into two sections. The corr fc'uit of the called' aci-ossi they line.V Tl

.l.. of any suitab'ledesign jtiong nector is provided with a differentially wound relay 14() which is composed of the windi'ngsl-ll and 142. The function of this relay is `toprovidcthe calling subscriber with talking battery current when the back bridge relay 143 energizes, 'and alsorin conjunction]witliithe vertical lii'ie relay 127, to control the ringer relay 114 by means of which -the 'ringer generator lli is bridged across the terminals of the called 'line'to sig? `subserilair. The 'back bridge relay 113, eoini'irisiiigthe `windings Hij/alud 1153, provides the ealledsubscriber with talkL ing battery 'current when tliefprin'laiy cir-- ie central station is ef'iuipped: with the busy sigiialing apparatus 'l as, for example, tlie'one comprising an "interruptor 147 in series with the primary winding 148 of the imluetion, coil V14A), whereby' a-busv signal- `ing current is indueedlin the secondary windiirg `150 of' t'hesaidin elietion eoih 'lhe sec'- ornlary winding lfliis connected with the side switch wiper 135 throught-he normal springs 1.71 and '1h12 ywhen the switch shyft is'raised and ther'side switch is in first 1165i- A clearer ifinderstanding of' my invention nia'ybe had 'by considering its action when one subscriber operates '-the centra-l oflice switches to call back on his own line. It

' substation bridged presses the line relay being'thus operated nei-m to trip to i eeond position',

desires to signal the subsi-friber at substation A',V in which event the se eetor switch allotted to the linexainductor '12T and 28 is operated to establ sh coniwetioi with the ring-ba`clt ariangeinentl) whieli'lfis allotted toithesecond level of the first sellertor banks. 'l`he subseriber at substation A removes the receiver from the switch hook 3.y whereby the springs 14 and l5 engage when the dial is turned. thus providing ground l'or the grouiu1 post lf3. Since the ring back arrangement `is allotted to the second `level of the first selector.\ the vertical line conductor 2T is given two ground impulses and the rotary line conductor 2H 4is given one. 'lhe impulsl to the vertical line eonductori'i causes the vertical line relay (i5 to be ener gized by a f low of current from the substation ground through the ground springs 11 and 15 tothe ground post '16, thence to the vertical impulse spring 21, vertical line conductor 27, side switch wiper 4H, Iii-st position contact point 53 to the line relay t5? them-ethi'ough said relay yand through the bridge cutoff relay springs 152-3 and 154 to the battery lead 1557 and through battery l5 to Vground (i. Vrl`lie line relay 65 into coi tact, -\\'hereb `a flow of `current is sent thiough the vertical magnet 66 from ground (i2 through the sa" and 157, private magnet springs 158 a'iid 159. veri ical magnet ff to thedmttery lead ane through battery l to ground (i. In a inlnner well understood the switch shaft is raised one step at a time7 whereby the shai'; wipers 15. 46 and 4T are raised to theisuv-ond bank levell opposite the `first trunk line thereof. l`he selector being thus opei ated, the iinpulseto the rotary line eond|uto- 28 eauses therotary line relay (-37 to energize by, a flow of current from ground il to the ground postfA 16, and through' t he rotary inijpulse spring 2:5 to the rotary lifie eoiu-luetoi the side iwitch wiljier 4i), contact pointlfl tothe ro" ary line :relay (37, tl Said I'elav and. through Vthe bridge` eut oil' relay springs 160, 153 and 154 to the battery had 155a l' i to groun l (L 'lhe said line.. relay (i7 operates 3o close' conneetion between the springs 1f1 and 15G5 whereby a flowof euri'ent is sent through the private magnet :72 from groi nd (12 ythrough'said springs' 15G and 161, t [rough said private Ii' |;'ig n` et o2 to the jbatterI lead 155, and through"v b attery liand to ground 't The [mirate .n'ia'gnet its'the' side switch at which time the side switel wiper 45.1 engages fthe grounded conta-et point G0, \\l|er( by a circuit is` es' tablished tirough the rotary magnet (iS-front ground (1 through said rotar )l magnet td springs 156 and 15T ld springs 156 ience 'through I and vtlirolngh battery li.

i the battery lead 155, and through B to ground (lr. begins to rotate the shaft, which latter then battery v car-rles the private wipery 47 onto the first contact of the second level .of the private bank. If the trunk line-leading from the 'first bank terminal ofthe second bank level is busy, the private wipIer 47 willfind the private contact grounded, since there is a selector similar to the selector C in connection with the first 'trunk line of-the second '-level, the private side switch wiper of which selector, similar t'o the side switch wiper 50,

t vis in third position and inengagement-with a grounded contact point similar to the con- ,tact pointl 63, Evidently, then, the guardingpotential is established at the privatebank contact throughthe described occupying selector by way of the' back `release relay of saidselec'tor, similar tothe back release relay 70. Therefore, as soon .as the privatel wiper 47l engages the said grounded contactmnenergizing circuit is established throughthe private magnet 52, which again energlzes and locks the side switch in second V,position in order to hold the energizing circuit for thev rotary magnet 68 until after the `shaft wipersl have been carried beyond the last busy trunk line and into engagement with some idle-trunk line.l -This energiz' ing circuit for the privatel magnet extends 'from the grounded private bank Contact through lthe private wiper 47, 'and' through the-back release relay 70 tothe side4 switch wiper- 50, thence (since said side. switch wiper is in'second position) through the private magnet 52 to the battery'lead 155, and through battery Bto ground G. As soon as the private wiper 47' has been advanced 4pc-by the 'rotary magnet 68 beyond the .last

busyor rounded` private bank contact, the

circuit tirough thej'private magnet 52 is a ain-broken,L at which time the side switch o the selector is' permitted to passte third position, at which 'instant the energizing4 circuitis' broken through the rotary magnet 68, and-the line. conductors 27 and 28 are ex- ,tendedto the line wipers 45 and 46 'which have previously engaged the trunk conductors 162 and 153; The subscriber is, therefore, .directly connected vvththe ring back arrangement- Not only is the subscribers' line thus extended, but al guard-ing potential is also/ established ati' the private wiper 47,.

when theside switch wiper 5.0 pa'ssesonto the groundcontact point 63, for'protectlng l the seized trunk line'against interference by other Icalling subscribers. This guarding..

potential 4is established from` groundfjG throughthe side switch -Wiper 50, back ref leasearelay,70,'conductor 164 to the private shaft isY given "avertical-step the normal-v wiper. 47 f Furthermore, when the selector arm 72 permits the sp1-'ing 73 to engage the grounded contact point 75, whereby a. guard- The rotary magnet then- `ing potential is established at the connector bank for protecting -the calling line against seizure by other subscribers. It will be seen,

`of course, that the energizing circuit for the rotary magnet'68, to which reference has alread lbeen made, is destroyed when the idle trun r line is seizedthat is, when the Side` switch wiper 51 leaves the contact'point 60.

The calling subscriber has now extended the conductors 27 and 28 to the ring" back arrangement lshown at D, and thel centralv y 'office switches occupy the positions indicated in Fig. 1. lVhen thesubscribers lines are thusextended tothe ring back arrangement D a circuit is 'closed extending from ground G5 through the'springs 165 and 166,v

through the winding 82 of the differential relay 83, rotary line relay 80, conductors'163 and 28,v primary winding andy transmitter of the substation to the vertical conductors 27 'and' 162, then through the vertical line relay 79 andrelay 167 in multiple, andthe winding 81 of thediil'erential relay 83`to the battery lead 155, and through battery B to ground (i. The line relays 79 and'80 energlze Aand separate` the springs they control, While the relay 167 energizes and? closes the springsit controls in contact.

. To slgnal the subscriber at substation A the calling subscriber at substation A presses the signaling-button'l, whereby the series circuit through the line relays 7 9 and 80 is broken; but an'energizing circuit is established through-thevertical'relay of the ringthrough battery B to grou-nld G. The relay 80, therefore, restores to normal position', 11obut the differential relay 83 energizes,'since one winding'Y only carries current. The relay 80' upon denergizing permits the springs A168 and 169 to .engage,.and the relay 83 upon energizing closes the springs 170 and 171 i-n contact. A clrcuit'tln-ough the ringer relay 85 is now completed extending from` ground G0; through the relay 85, springs'168 and 169,

springs 1-70 and 171 t'd the battery lead 155, and through battery B to ground G. The ringer relayI 85 thereupon energizes and places the springs 172 and 173, 174 and i175" in contact, whereby the terminals ot the ringer generator E a-rejbridgcd .fycrss the conductors 162 and 163 A signaling current then' passes rom the generator Fi through the springs, 74 and 175,` onduttors 163, '28 i l and 176, springs 178 and 1%79; ringer 180 and condenser 181 to the c( ilductors 182, 27 and 162,v springs 173 and 17 back tothe gerras soon as the ringing key at substation A is returned to normal over a circuit extending from ground G5 through the springs 165 and 166, through the winding 82 of the relay 83,

rotary line relay 80, tl'irough the conductors 168 and 28, then through the primary .windings 1f.) and 183, transmitters 17 and 184. to the vertical line conductor 27, side switch wiper 48, shaft wiper L15, conductor 162, through the vertical line relay 79 and relay 167 in multiple, and winding 81 ofthe differciitialrelay 83 to the battery lead 155, thence through battery B to ground G; The wind ings 81 and 82 of the relay 83 are soarranged that when both windings carry cury rent, `as before explained, the said relay does not operatively energize. The two substatioiis being thus provided with talking current, conversation .may lie carried on in 'the well known manner. After the subscribers have finished their conversation the subscriber who last restores his receiver to the switch hook brings about the release of the central oiiiceswitching. al'iparatus, as fol lows: Suppose suliscriber A restores his ref ceiver last. In that 'event the cam-arm 4 `presses the release springs 7, 8A andi!) into contact inoinentarily,` whereby Vthe vertical and rotary line conductors" are simultaneously grounded. The grounding of the rotary line conductor 28 short circuits the winding 82 of the differential 'relay 83, whereby thesaid relay becomes unbalanced and operates to shift the spring 171. .into engagement. with the spring 170. Thus far, however, nothi'nglias occurred to initiate the release, but when the ground is removed by.

the disengagement of the release springs-7, 8 and 9, the last energizing circuit established is broken and the vertical line relay 79 and relay 16.7 deiinergize. The relays 79 and 167,

as shown, are both slow acting relays, but the relay 167 is slower to restore to normal than the relay 79; hence, when the springs 185 and 186 cngage,`be'fore the sl'irings 187 and 188 disengage, an energizing circuit is` closed through the backrelease relay` of the selector switch C, 'si'.iidcircuit extending from ground (i4 through the back release relay 70, conductor 164, shaft `wiper 47, dead resistance 84, 4springs 185 and 1 86, springs 187 and 188 .to the battery leadil, thence' through bittery B to ground. G. Tlie`back` release relay`7() upon energizing places the Ifrom substation ground G throughfthe very springs 189 and 19() in contact, whereby an energizing circuit is in turn provided for the release magnet- 69, this circuit extending from ground G7 through the springs 189 and4 190 and thro igli the release magnet 69 to the battery lead L55, thence through battery B to ground 4. All of the relays and magnets thus eiiergizi d attract their respective armatures and remain inV readiness to return to normal position as soon as the relay 167 deenergizes andthe slirings 187 and 188`disengage. In th s releasing operation it will be seen that the grounding of the two sides of the ,line by ihe hanging up of the receiver has no pa rtizular function. It is the denergization of the relays 167 and 79 which initiates the release and these relays do not` denergize until the last subscriber has hung up to open the last bridge across the line. It the subscriber at ysubstation A, however, desires. to establish connection with a] subscriber or some other line, the selector C is operated tf. seize some idle trunk line leading to a. conn actor or to another selector', and finally. to a (onnector, which is operated to establish cor ricction directly with "the desired line. ber 320 (sul station A2) the subscriber at substation A removes his receiver from the switch hook ind operates the calling device Alor example: To call the numi y once for eacl digit in the well-known manner. When ihe device'is operated for the .first digit the first selector switch C is operated to establish connection with an idlel g trunk line lea ding to-the connector switch F; The impulses for the last two digits are directedI towarc the connector switch F., which .Y

pulse spring 21 Vis pressed onto the ground i post 16 three times. As a result the vertical l'iiie relay 65 of the first selector C is energized each'tin ie by afiow of currentV f-rom the substation griund through the vertical li-ne relay 65 to ',he battery liz-ad 155, as previously eiiplained.V The vertical line'relay ir. turn opeiates to energize the vertical .magnet 66, whereby the shaft wipers are Q raised opposte the bank contacts of the"` thirdy level. l `ollowing the vertical impulses the rotary lii e relay 67 'is energized as be` fore, and-the private magnet in .tnrn oper' ates to carry the side switch fromfir'st to secg' ond position,- Nhereby the' rotary magnet becontes energiz ed, and the shaft Wipers 45, 46` and47 are operated toselect an .idle trunk line leading to the connector switch F. The

grounding of the line condlictoi's 27 and 28 for the last t` vo digits affects theconnector by operating f `he vertical and rotary line re- `lays 127 and 128.

conductor 27 is grounded the -vertical line* relay 1.27 is energized by a flow of current tical line con :luct-or'. 27, side switch` wiper When the yvertical line the' relay 140 to thel battery lead 155, thence the shaft wipers 124, 125 and 126 in a vertical direction one step at a time until the said wipers are carried two steps and thus brought opposite a level in which are located the terminals of the'line :#:320- 'The circuit yao vsa

through the vertical magnet 129 extends from ground Grs through the springs 192 and 193, vprivate magnet springs 194 and 19.5, side switch wiper 136, vertical magnet 129 to the battery lead 155, thence through battery B to ground G. Vhen the rotary line conductor 28 is .grounded following the grounding of the vertical line conductor, the connector rotary line relay 128 becomes energized through a circuit from ground G' to the rotary line conductor 28, side switch wiper 49, shaft wiper 46, rotary trunk conduetor 196, rotary line relay 128,-winding 142 of the differential relay 140, through 'the springs 197 and 198 to the battery lead 155, thence through battery B to ground G.

AThe winding 142 of the differential relay 140 being included in this circuit, said relay 140 energizes, but with noeffect; The rotary line relay 128 upon energizing operates to close an energizing circuit through the private magnet 131, which latter in turn operates to release the side switch from first to second position. -For the last digit the subscriber operates the calling device as previously described, grounding the vertical line conductor 27 ten times and the rotary line conductor 28 once.- The vertical and rotary line relays 127 and 128 are operated over previously traced circuits. However, when the vertical line. relay operates, a circuit is closed through the rotary magnet 130 instead of through the vertical magnet 129, since ythe side switch wiper 136 is now in second position. Each time that the rotary magnet is energized the shaft wipers 124, 125 and 126 are rotated one step at a time until the said wipers are carried into engagementwith the normal conductors 1988, 199 and 200, the rst two of'which lead to the line terminals ofthe desired substation. The rotary line relay 128v upon energizing completes an energizing circuitl through the private magnet 131 as before, which latter now operates with one of two results, namely the release of the side switch from second to third'position, or the so called busy release of the con'-V lt will be assumed that the former nectar. result occurs, and that the side switch passes to third position, whereby. the side switch wipers 134 and 135 are placed in connection with the' shaft Wipers 124 and 125, respectively. Furthermore, when the side switch passes to third position a guarding potential is established for protecting the called line. This potential extends from ground G through the side switch wiper 137 to the shaft wiper 126 which engages the private bank contact of the seized line. Furthermore, when the side switch passes to third `position an energizing circuit is closed through the bridge cut-off relay 151a of the first selector Aswitch H.. This circuitJ extends from the guarding potential ground G to the shaft'wiper 126, normal springs 152a of the lirst selector H, through the winding of I switch wiper A136 is in engagement with the third-position contact point, thereby placing the vertical line relay 127 in control of the ringer relay 144 in the same manner in whichthe rotary magnet 130 came under the control of the vertical line relay when the side switch passed from first to second position. Therefore, when the vertical line relay presses the springs 192 and 193 into con-` tact, thel ringer relay 144is` energized from ground GrE through lglie springs 192 and 193,

private magnet springs 194 and 195, side switch wiper 136, ringer relay 144,v springs 201 and 202 (bearing in mind that the differ ential ,relay 140 is energized) to the battery lead 155, thence through battery B to ground G. The ringer relay upon energizing opcrates to bridge the terminals of the ringer 4generator E across the conductors of the desired line. A signaling current is therefore sent from the ringer generator H to the substation rnger 203. In response to the signal the subscriber at substation #320 removes Y i his receiver from the switch hook, `whereby,

the switch hook rises, permitting thewsprings 204 to disengage and the springs 205 to engage, 'thereby removin across his line' and ridging insteadg the transmitter and primary winding. When the primary winding and transmitter come the ringer 203 'from y across the line an energizing circuit is established through both* windingsof the rela 143, said'circuit extending from ground Gl; through the 'side switch wiper 137, through the winding 146 of the relay 143through the ringer-relay springs vand side switch wiper 135 to the rotary -normal conductor. .199, rotary line conductor 206, through the primary winding and transmitter to the vertical line conductor 207, vertical normal conductor 198, shaft wiper 124 and side switch `wiper 134, through `the winding 145 ofthe .relay 143, through` lthe springs 208 and 202 to the battery lead .155, thence through bat tery B to lground The relay 143 upon energizing operates to shift the spring 197 from the spring 198 f(which latter* is connected with the battery lead y155) to the spring 209,'v`which. in,v turn is connected with ground. The revcrsalof polarity in the spring 197 .sets 'up a circuit which provides the calling subscriber with battery current for talking purposes. This circuit may be traced,` from.,f groiind'Ui through the side 4switch wiper 137, springs 209 and 197,

. through the winding 142 of the relay. 140, rotary line` relay 128., condilctors 196 and 28,

through the primary' winding and transmitterofsubstatin Ato-,the vertical line conductors 27 and 191, vertical line relay- 127,

winding V111 of the diferential relay 140 to the battery lead 155thence through battery. Btoground (lr. Both windings of the relay llJr() now .carry current, but the windings are so arranged. that the said relay does not operatively energize. The vertical and rotary line relays 127'and128, being included in -theabove circuit, operatively energize and placetheir springs in contact, and the release springs 210 and 211 are also brought into contact, but the simultaneous action of these relays-at this particular `time is without eifect, since; no energizing circuits are established thereby. The'two-substations A and A? beingithus provided with battery current for talk-ing purposes, conversation may be carried on over circuits shown by the heavy line conductors inFi'g's. 1 and The release ofthe 'central office switching` apparatus Iis broughtabout when the calling subscriber restores' the receiver 2 to the switch'hook 3, thereby pressing the release springs 7,8 and 9 Vinto engagement for a nioment. The contact` of' the said release springs grounds the vertical and rotary line conductors: 27 and 28 vsimultaneously from ground G to the release spring 7, thence through the springs 8 and 9 to the vertical and rotary line conductors.

of the rotary 'lineconductor 28 produces a shortfcircuit ofthe rotaryline relay12'8 in series.Y with the winding 1&2 ofthe diiferen-- -tial relay 144:0` Thejsaid circuit extends frein ground .G9 at the Kconnector to the side switch wiper 137,l springs 209. and 197, through the,.,winding 142. rotary line relay l128'. conductors 196 and 2,8, through the release ysprings..9, 8 and 7 to thc substi'ition4 ground Gr', Therefore, since the winding 1'711 of..ftlie differential relay .140 alone carries durrent,y the said relay. .becoinescnergized` and attijactsitsV armature, which shifts thespring 202out of contact with. the spring 2(18ffaiidv .into Contact with the' spring 1.,.

The grounding The disengagement of the springs 208.and1.

202'dest1'oys the energizing circuit through the relay 143, and the spring197 passes out of engagement with the-spring 209 'and into. engagement .rith the spring 198, which 1'emoves the s: id' short-circuit of thc 4rotary line relay 125 and winding 142 and cstiihy lishes an energizing circuit instead from the substation ground through the release springs 7, S i nd 9 to the i,'otary line cond pci tor 2S, thcnci tol the rotary line relay 128(15 previously tr iced, winding 142V otl the dilf'clf ential relay 110throiigl`1 the springs 1917 and 19S Vto the battery lead 155,.then`oe through batti ry B to ground "The rotary line relay 12E now operates, and the springs 210 and' 211 come into contact. u-zhcrcby an energizing ci 'cuit is established through thc, release niagnft 13 2 of the connector F and the release rc ay of the selectin-C, .Howcve'r. thc. current now in passing, as above stated. through the .winding 142 aids the winding 141 n maintaining thersprings 201 and 202 in contact., T he energizing circuit 'through the release magnet 132 extends from ground 'G4 at the selector C through the side switch wiper 50,'back release relay '70, shaft wiper 47. con luctor 212, through the release springs 210 and 211,` release magnet 132,

.springs 201 aiid202 to the battery lead 155,

thence throng,i h battery Bto ground G. The

connector. rel ease ii'iagnet, upon being supplied with cir-rent. energizes, and as a result to normal condition, thus breaking the con# the vswitclifshiiftand side switch are restored nection betwi en the connector switch' sha'ft wipers 124.125 and-121i and .the norm'al e011-,

dilcto'rs 198, [99 and 200. The back-release relay 70. being nhthe saine circuit with the release niagni t132. encrgizes simultaneously `with thelatte r and Voperates to close the. cir-A uit through the. release magnet ('Sl'of the selector C l; y pressingv the back-release springs 189 ind 190 together. through the=i eleasemagnet69 extends from The circuit s groundtlr7 th foiigh 'thc springs 189 and.190, j

and through the release vinagnetfl to y the A buttery-lead "VhenJthe ground to'the line'conductofs 27 and 28 is interrupted all."

t-he magnetsgniolved 4intlie release are de' energized angl all switches fully '1.i;e storccl. The ring-,baci arrangement DV shown in i Fig.y

2 is a modified forni of D shown in Fig; 1 to;

`this extent, ni'mcly that' fthe sloi'v-,acting relay 167, instr ad o f being in multiple-with the linc relay 79is controlled bythe line; rel layMthat is, i .'.hen the-line relay '79,energ1zesA itcloses a crcnit through the relay 1.67v

which encrgiics and placesthesprings controlled tl'ici'elzy `in contact. y Now, when the line lrelay .79 deenergi-zes; the springs and 1851. eng .ige andI close the release. circuit,4 sincethi. relay' 167 is still inlan'` operated'A position. .When'the relay l167. dene'rgizes, the rele use' circuit broken.-

'rac

Fig. 2, is'similar to D, Fig. 1. Freni the foregoing `it will be seen that I provide a commonba'tter'y system in whichy party line subscribers uniformly call the subdetails and featuresfthe.arrangement at D,

scribers on thc same line by a single movement of the calling dial. The ordinary comnion battery connectors having ringer relays can be employed for calling and signaling between different lines.' The said rin v-back arrangement not .only controls the ow of both ringing and talking current to thesubstations of the p aigty line, but also controls,

the trunk-'release'l circuit extending back through the-'first selector .in 'the manner explained.

It will be seen that one of the principal' advantages of my invention is that in a common battery system having a ring-back arrangement of.this kind the party line subscribersare furnished with a ring-back arrs'mgement, andk the system is such that further pressure of the ringing key at the calling substation, after the called subscriber has answered, vwill not release the connection notwithstanding that `only i two wires are 'used between the different substations of the party line.

What Il claim as myinvention is 1. Inatelephone system, release mechanism therefor, a' trunk release` -circuit, a talking circuitf a plurality` of timed slow-acting relays control-Y diferently lin said 4releasel circuit, andv a circuitv for said relays in part coincident With both sides of said talking' circuit in series.

2. -Ina telephone system, suitable switches,

release mechanism therefor, a trunk-release I circuit, a talking circuit, a pair of differently timed slow-acting' relays controlling normally .closed and normally onen switch points' in said: release circuit, and a. circuit for energizing-said relays in multiple, `said energizingcircuit b eing in part coincident with both sides of Qtlie talking' -circuit in o lling--sa'i ys are energized overg'the .two sides of the talking circuit in'series.

a telephone system, =a line circuit, switches, release mechanism thereofsaid lrel 'suitable for La? trunk-release circuit, a phi'ralityof di erently timed .relays controlling said `reuicker of said relayswhen opent.

, oSQet. sam opened-bythe dee'nergizing4 ofthe other o r'. slower of said relays. Y

suitable switches',

pair of conductors,

r-releasecirciiit, a talky f ing circuit, and' connections whereby both vid release.-cir-` ...sul leasecircuit' 'beforefthe in series.

6. In a common battery automatic telephone exchange system, suitable switches, release.'mechanism therefor, a trunkrelease circuit, a talking circuit, a 'plurality' of differently timed slow-acting relays controlling said release circuit, a circuit for said relays in part coincident with both vsidesof said talking circuit in series,"and .a central source of iurrent connected -to supply talkling current through the' windingof one of said relays.

7. In a common' battery phone exchange system,

automatic telecircuit, a talking circuit, apair of differently timed slow-acting relays controlling normally closed and normally open switch points i'n said release circuit, a circuit for 'energizing said relays in multiple, said 'energizing circuit being in part coincident with both sides of the talkingcircuit in series, and a central source of .current connected to supsuitable switches, l release mechanism therefor, a trunk-release plytalking current through the winding of one f saidrelays.

8. n a 'telephone system,

a substation for vsaid line bridged across saidA conductors, means -in said bridgefor talkiigover said lines, a progressively movable switch, release a line having .a

mechanism for said switch, a circuit for..

controlling the operation of said release `mechanism,'a plurality of other lines,a set s as ated with first line is connected, onv

Y of said. relays energized over two sides of Said talking vcircuitin series.

9.. In a'common release mechanism therefor, circuit a 'pluralityof di af trunk-release nergiedj sides-pf the -line circuit in ser1es,'=\whereby the opening of the line circuitcausessaid battery automatic tele- .phone exchange system, a line circuit, suit- -able switches,

ingQthe said circuit tov vthe set of relays -associatedwith the other line to which said relay to close the release circuit before thev 15. In a tehphone system, a party-1i`ne same is opened -by the denergizing of the having a pluri' li'tyof substationsthereon, other or slower ofsaid relays, and a central arring-back a 1i paratus, means for extendsoui'ce of current connected to supply talking connection from said-line to said ap- 5 ing current through the Winding of'one of paratus, a line relay and a differential i'e- 70 said relays. lay, means for energizing said line relay,

10. In a common battery automatic teleand iiieans foi signaling the called subphoneiexchange system, a line, a plurality scriber over said connection by h'rst denf of s ubstationg thereon, a ring-back. appaergizing said line relay and than' energizratas, and means for extending connection ingr said dili'ereltial relay.

' from said line to said apparatus, the vsaid l( In a telephone system, ,a partyL-line apparatus comprising means responsivei to h avinf #pr plural ty of substations thereon, a the opening of the line for releasing the con r1ngf' ck appa utils, means for extending vn ection, consisting of two differently timed coneotlon" ron. said line to said appararelays, a release circuit having-'affswitch tus, fi-"Jine relay and a dilferential relay 80 point closed by the denergizing of the included in a bridgeacross said circuit,

' quicker of4 said relays, av switch point means for eneigguzirig said line relay, and opened by-'tlie denergizing 'of the slower means for signaling the called subscriber of said' relays, a circuit for. energizing over s ald conne etiorrby---jfirst denergizing.

tliesaid quicker relay-over the two sides of said line relay and then .energizing said 85 t the-linein series, and a central source of differential relay 'current connected to supply talking cur- In a tele] f hone systenu 'partydine rent through the windingpf `one of said 'harinar i, plurality of s'ubstations thereon,

relny a ringband; api'aratus, n'ieans for extendgll. In-'a common battery automatic tcle- 111,9; connection "roin said lin'c'to said ali- 9,0

phone-exchange systema party line haijing parat-us, `a pair o frelays, and means for a plurality of substations thereon, a ringf- Signaling over said connection by dencrback apparatus, means for extending conf gizing'one of 11d relaysl by4 4opening the necton ,from said line to said apparatus, .hac circuit and tien energizing theother of sponsiv'e to the opening of the liner-circuit mie system, a party-line for releasing said'connection, and a common""hlfi1ng a pluralii y of. substations thereon, a-

battery 'forfurnishing talking current. ring-back apparatus, means 'for extending .85 through' said lastinentionediinearis connection from :aid line to said apparatus, '100.

i 12. In 'a telephone system,.a pair of line a pair Vof linerelaysand a differentialrefrelays, a slow-acting relay supplemental to lay included in a bridgelacross said line cir- Ione of said relays, a trunk circuit controlled .Cult .lnelnS for Signaling over said conby said line relay and its supplemental renection, and, means controlled by one of 440 lay, a Vringer relay, a. double.Wound relay said line relays i nd said differential relay ,106

connected in series-with said line relays, for controlling sa 1d signaling means.v I ,and a circuit through 'the ringer relay leon- 1 9. In a telephone system, subscribers trolled bythe doublelwound relay and the lines, a .calling and a called` subscriber-,a other line relay. line. relay and a diierential'relay bridged 13. In a' telephone system, suitable'across said line, and means controlled by 110 switches, a; pail" of` 'line relays, a -slowthe vcalling subscriber "to signal the called f'actngvrelay si'ipplemental to oneof saidV subscriber: by lint` denergizing said .line

Y "relays, a-/trunk circuit' controlled bysaid relay'by 'opening his line circuit andithen line relay and its supplemental relay," a groundingr one limb of bis line 'to'thereby ringer relay, a doublewound relay,` a cip `.energize said d ilfrential relay. v 115 cuit"throughthe ringer relay .controlled by 20. In a `telepl one system, calling and:

.the* d0ub1e.-W0u nd relay. and the'orher line called' subscribers, means for establishing.. relay,'a release relayin said trunk circuit, a talking conneiton between said subrelease mechanism .controlled by' said rescribers, a vpair (9' relays, and` means for f lease relay,' andV line circuit excludingr said first dencrgfiziiigr one of said relaysandthn 120 trunk circuit. energizing the oiher of said relays" for 14. .In a telephone system, a party-line jointly controllingl the application of sighaving a plurality of substations thereon, a naling current to said called subscriber. ring-backapparatus, means for extending 2L ln' a telephrne system, a subscribers i connection from said line to 'saidapparatus line, a plurality oi .stations on said4 linefan- 1.25

' the-"said apparatus comprising means for other Iine,a' siyiicli having progressiifely' .signaling over said connection. a differential movable wipers foi' connecting said first line relay connected toone limb of the line, angl with said other lire, ay line' relay and a difa line relay connected to the otherside of the iferential relay :for :aid other line, aud'ni'eans `30 *1 for line for controlling saidsign aling means.

under the control( f one of said stations controliing said rela s jointly to apply ringing currentto anot er of said 'stations by f 'way of said Wipers.

22. In a telephone system, aline having a pair of conductors, a. substation for said line-bridged across said conductors, means -in saidvbridge fortalking over said line,

other lines, a progressively movable switch `for selecting and connect-ing with any one ofjsaid other lines, rele-ase mechanism Afor said switch, a plurality of differently timed relays individual to earh of said other lines for controlling 'said release mechanism, said relays energized over the two sides of said talking circuit in series.

23. In atulephone system, a line. a ]nogl'vssively 'movable switch "for said lino, :1nother lille. lneans'for operating said switch to eonnevi said -irst 'and serond lines, releaseA means for rel asinf' said sn'itvh, and a pair of inagnetshavlng different time constants for (-,ontrolling said release means1 said-l'nagnets energized hy currentover said "24. ln a telephone system, a. line, a 1n-ogresslvely movable swltvh lor. said line, anotherr line, means for oi'xfrating. sald switch to connect said first and second lines, release means for releasing.' said switch, and a pair of magnets having different time constants for controlling said release means, said mag'- nets energized by current over said first line,

said magnets individual to said other line. r25. In n telepliomx system, a hne havlng a YVairoi" conductors, a substation for said line )ridged across said conductors, means in said bridge for talking over said line, a progressively movable switch, release meehanism for said switch, a circuit for con trolling'the operation of said 'release meehanisni, a plurality of other lines. a setof differently timed relays,assofratedivith Isaid I J. M.A CARGO. 

